In gliding, a pilot seeks to take advantage of thermals, or up-currents of air, and conversely to avoid sinks, or down-draughts. By skilful utilisation of thermals, the gliding time may be greatly prolonged.
On approaching one side of a thermal, the wing on the thermal side should bend more than the other wing, even if only for a short time. To detect this strain gauges might be cemented to the wing spar stubs of a glider.
A difficulty with this approach is that when the strain gauges are applied to the surface of the wing spar stubs and this surface consists of fibreglass (or other) rovings that have a protective as well as a structural function, the strain recorded is not always directly related to wing bending. To overcome this the strain gauge could be set in the material at manufacture. Another practical difficulty with this approach is that since the wings are removable from the fuselage and the strain gauges are attached to the wings, a tedious system of electrical pin type connectors must be coupled for rigging and uncoupled for de-rigging.